Skip to main content

Full text of "Practical Organic Chemistry"

See other formats


The various reactions, known as the Friedel-Crafts reactions,
arc effected by means of anhydrous aluminium chloride.    The
aluminium   chloride,   being-  very  hygroscopic, cannot  be kept
long, even in a stoppered bottle,  without undergoing- gradual
decomposition.    As the success of the reaction depends entirely
on the quality of the chloride, it should be either freshly pro-
cured, from a reliable firm or resublimed from a retort.    It may
also be prepared on a small scale by passing dry hydrochloric
acid over heated aluminium foil or filings, but the operation is
troublesome  and   scarcely  repays  the   time  spent.    Attach  a
round flask (500 c.c.) to an upright condenser, and bring into it
the aluminium chloride, which should be well powdered, and
immediately cover it with the benzene.    Place the flask in ice-
water, and add the acetyl chloride drop by drop from a tap-funnel,
which  is pushed into the top of the condenser.*    A vigorous
effervescence  occurs,  and hydrochloric acid is evolved.    The
contents of the flask are converted into a brown, viscid mass,
which, after standing an hour, is stirred up and shaken into a
beaker containing ice and water (250 c.c.).    The mass decom-
poses with evolution of heat, and a dark oil separates on the
surface.    The liquid is poured into a separating-funnel and a
little benxene added.    The aqueous portion is drawn off, and
the benzene layer shaken up with dilute caustic soda and then
with   water.    The benzene   solution  is  finally  separated,   de-
hydrated   over calcium   chloride,  filtered,  and distilled.    The
benxene first passes over.    The thermometer then rises quickly
to 195°.    The receiver is now changed, the water run out of the
condenser, and the distillate, which boils at 195—200°, collected
separately.    It forms  a  pale  yellow oil with a characteristic
sweet   smell,   and   solidifies   completely  on   standing.    Yield,
20—25 grams.
C(;H(J + CH3COCl = CUH6.CO.CH3 4- HCL
Properties.—Colourless plates ; m. p. 20° ; b. p. 202° ; insoluble
in water.
Reacfi<ws*—i. Acetophenoneoxime.—Mix together 5
grams of hydroxylamine hydrochloride dissolved in 10 c.c. of
water, 8 grams of acetophenone, and 3 grams of caustic soda
dissolved in a very little water. Add spirit until, on warming, the
solution becomes clear, and boil it on the water-bath 2—3 hours.